Handle-bar stem



Patented Sept. 5, 1944 UNIT-'ED STAT E S PATEN T OFFICE HANDLE-BAR VSTEMFrank W. Schwinn, Chicago, Ill.

Application December 18, 1940, Serial No. 370,634

.2 Claims. (Cl. 287-54) The present invention relates to a handlebarstem for bicycles and is particularly'conce'rned with the development ofan improved handlebar stern and a simplified and improved method ofmaking such stem.

In the manufacture of bicycles it has been customary to forge the-blanks for the handlebar stems to a formapproximating-thei-r finalshape. rIhis shape included a straight cylindrical lower portion, and anangularly disposed upper portion. This bar was subsequently formed, bysuitable grinding, drilling and slotting operations, into a handlebarclamp.

The finished handlebar stems are highly polished and plated, and, in theprior construction of such stems, the machining, polishing and plating voperations performed thereon, were necessarily numerous and difcult, andwere not adapted vto low price, large quantity lproduction methods onstandard types of machines.

The forging of the blanks approximately to the shape of the finishedstem required a large number of forging operations with the result thatthe blanks were frequently pitted, so that it wasnecessary to form theblanks with a relatively large excess amount of material whichsubsequently was removed by machining.

' It is difficult to discover hidden' flaws and Yweaknesses in a forgingthus formed, and since the breaking of a handlebar stem in'use is apt tohave serious consequences, increased assurance of freedom from suchhidden imperfections is of extreme importance.

An object of the present invention is to simf plify 4and improve themanufacture of bicycle handlebar stems.

Another. object is to develop an improved handlebar stem from a simpleblank with a minimum number of operations and maximum characters ofreference indicate similar partsthroughout the several views.

Referring to the drawing, of which there is onesheet,

Figure 1 is a view'v in perspective of aforged blank for -a handlebarstem made accordi-ng .to-

the present invention, the flash from a forging operation having beenremoved therefrom;

Figure 2 is a View in side elevation of the blank shown in Figure 1,after machining, an end po-rtion thereof being lbroken away to show alongitudinal sectional View through the center of -a hole therein;

Figure 3 is a View in perspective of the machined blank illustrated inFigure 2 after forming to final shape;

Figure 4 is a plan View of the formed, machined blank shown in Figure 3with a bolt hole drilled therethrough; and

Figure 5 Yis a vertical longitudinal sectional View through a completedstem having its asso- Vciatred parts assembled therewith.

In Figure 1 of the drawing, the numeral -II indicates generally a forgedblank made according to vthe invention a'fter the trimming of vthe ash,not shown, which projects laterally from substantially the horizontalmedian plane -of the leted vand of cylindrical section with a radius o-fcurvature approximately equal to that of a handlebar I 6, such as isshown in Figure 5. Each of the fillets which comprise the curved ends ofthe depression I5, has a circumferential length equal to approximatelyone-fourth of the circumference of the handlebar I6 with which thevstern is to be used, while the length 4of the intermediate flat portionis equal in length to slightly less than one-half of the circumferenceof such handlebar vwhen bent to finished form.

The plane of the bottom of the depression I5 is tangent to the curve ofeach of the ends of vthe depression so vthat when the head I4 of thestem is formed by bending to the shape illustrated in Figure 5, it willconform to the shape of the handlebar I6.

The head I4 has two holes I'I and I8 therein one in each of the thickerend portions of said head, said holes preferably being punched while cthe piece is hot as a part or continuation of the The hole I'I is formedwith-a' forging process. pair vof laterally extending kerf-like recessesI9, as shown in Figures 3 and 4, toreceive locking shape.

, mately 90 degrees.

fins 20 on a bolt 2| used to clamp the handlebar I6 in the finished stemas shown in Figure 5.

It has been customary in the manufacture of handlebar stems, initiallyto forge an oversize blank substantially to form, and then to grind thepiece to size. The ground blank was drilled and slotted to provide thehandlebar clamp, and the piece was then polished in three successivepolishing operations, each of which was performed with a nner grainedpolishing medium than the preceding one, so that each polishingoperation removed the line scratches left by the preceding operation. Y

In making a handlebar stem according to the present invention, it ispreferred to perform the grinding operations and the first two of suchpolishing operations while the piece is straight, as shown in Figures land 2'. The cylindrical stern I2, and tapered neck portion I3, being ofround section, are well adapted to rapid, inex- 'I pensive machinegrinding and polishing on .ishing operations, as above set forth, thereduced thickness, recessed portion I of the head I 4 is bent beyond theelastic limits of the material thereof around a mandrel, not shown, ofapproximately the samel diameter as the vhandlebar I6 to form ahandlebar clamping eye. As a result,

.the fibers of the material in the reduced thickness portion I5 are sostretched and re-alined in the outer peripheral part of the clamping eyeand compressed in the inner peripheral part of the eye that it will notspring back to the straight form but permanently retains the curved eyeThe portion of the head I4 having the recess I5 therein, is of a lengthso proportioned to the circumference of the handlebar I6 as to leave aspace 22 separating the head portions having the holes II and I8therein, as illustrated in Figures 3 and 5, thus permitting the headportions to be drawn together by the bolt 2l for tightening the clampthoroughly to the embraced portion of the handlebar.

The tapered neck portion I3 is bent laterally toward the side of theblank having the recess I5 therein, the bend in the present illustratedconstruction being through an angle of approxi- Both of the abovementioned bending operations are preferably performed While the piece iscold. If the blank is free from defects or hidden weaknesses, such coldbending will not affect its strength, but if a serious defect or hiddenweakness exists, the piece will fail or will tend to kink at the pointof flaw and maybe scrapped. The bending of the piece to shape thus actsto test the blank for flaws.

A hole 23 is drilled lengthwise through the cylindrical portion I2 ofthe bolt, being continued in a straight line upwardly and through a sideof the neck portion I3 as shown in Figures 4 and 5. The lower portion 24of the hole 23 is counterbored to permit a slight lateral'movement of astem bolt 25, and the upper end of the hole 23 is also enlarged as at 26and is machined to provide a flat face 2'I as by means of an end mill,not shown.

The stem bolt 25 is provided with an enlarged cylindrical head portion28 adapted to rest on the face 2'I and to extend upwardly beyond thecounterbored portion 26. The upper portion of the head 28 of the bolt 25is of hexagonal shape as at 29 to permit turning the bolt with a wrench.

The lower end of the stem I2 is cut off at an angle acute to its axis asat 30 to provide a cam face to cooperate with a similarly disposed camface 3| on a conventional wedge member 32.

The wedge member 32, which is preferably an aluminum die casting, is ofcylindrical shape, of approximately the same diameter as the portion I2of the stem, and is made with an internally threaded bore 33 to receivethe bolt 25 in a conventional manner.

The present structure is cheaper and easier to manufacture than theconventional type of handlebar stem for a number of reasons, as well asbeing less apt to have hidden flaws or defects which might result infailure of the stem while in use.

A considerable saving in material is accomplished because of thepracticability of forging closer to finished dimensions as above setforth, which in turn has the desirable result of requiring the removalof less material to attain the nished dimensions. The handlebar boltholes may be punched instead of being drilled as in the priorconstruction, while the drilling of a hole and the milling of a slot forthe handlebar clamp are eliminated and replaced by a simple bendingoperation.

These advantages are of course in addition to the important advantageswhich include the simplication of the grinding and polishing operationsachieved by my invention, and the cold forming to shape which disclosesany dangerous hidden aws or Weaknesses in the forging.

While the description of the illustrative embodiment of the inventionhas been based on the making of the blank by forging, it will beapparentA to those versed in the art that the blank can be made by othermethods, such as by the machining of a blank bar or billet of bendablemetal such as steel, and cutting or formingr such piece of metal'to theform of the nished blank, such as that illustrated in Figure l, by meansof suitable machining operations.

The forming of the machined or partly machined blank to shape by thebending of the upper portion of the stem to offset the clamp from itsoriginal position of alignment with the lower or main portion of thestem, produces a structural change in the metal of the stem itself whichconstitutes a slight stretching of the metal on the outer side of thebend, and a tendency toward the compression of the metal on the insideof the bend. The set-up of these stresses causes a rupture ordeformation of the blank at the areas of bend incase of a rejectionablenaw in the piece.

The grinding and preliminary polishing operations above referred to,which are performed upon the piece while in the original or straightform, are preferably performed while the piece is being rotated, `andAWhen so performed, the finish producd upon the blank is substantiallyuniformv throughout the entire area of circular cross section. Thischaracteristic produces a uniform polish on the entire area after thepiece is bent to nal shape, as illustrated in Figure 4,

and greatly facilitates the final polishing operation prior to plating.

While I have illustrated a preferred embodiment of my invention, manymodications may be made without departing from the spirit of theinvention, and I do not wish to be limited to the precise details ofconstruction set forth,

but desire to avail myself of al1 changes within the scope of theappended claims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States, is:

1. A handlebar stem comprising a body of originally straight bar stock,but in the nished form having a substantially gooseneck shape, includinga straight cylindrical lower portion adapted to lit within the fork stemof a bicycle, a head return bent and internally dimensioned to embrace ahandlebar, the end portions of the head being in opposed spacedrelation, means for drawing the opposed portions of the head together toeffect tight frictional engagement between the head and the handlebar,an integral intermediate portion extending as a continuation of theupper end of the lower portion and of one of the end portions of thehead, angularly to the axis of said lower portion, and laterally spacingthe head therefrom, and means for securing the stem in the fork stem ofthe bicycle including a stem bolt extending axially through said lowerportion and having its head accessible to a wrench at the upper end ofsaid lower portion.

2. A handlebar of substantially gooseneck shape comprising asubstantially straight lower portion adapted to t within the fork stemof a bicycle, a head which is return bent and internally conformed anddimensioned to embrace a handlebar, aligned apertures in said superposedspaced ends of the head', a bolt occupying said apertures whereby saidends may be drawn together to effect tight frictional engagement betweenthe head and a handlebar embraced thereby, a curved intermediate portionintegral with the straight lower portion and one of the ends of the headand serving laterally to space the head from said straight lowerportion, and means for securing they stem in the fork stem of a bicycle,said last-mentionedv means including a stem bolt extending axiallythrough said straight lower portion and having its head accessible ,to awrench at the upper end of said lower portion.

FRANK w. SCHWINN.

